1. Field
The systems and methods described below relate to the detection and scoring of calcium deposits in an artery, and more specifically to using an anatomical model image to improve detection, classification and scoring of coronary artery calcium.
2. Background
Medical imaging is the field of creating images of the human body for medical purposes, such as diagnosing or examining disease or other physiological anomalies. Numerous types of image modalities produce medical images, such as magnetic resonance imaging (MRI), radiography (x-rays), computed tomography (CT), ultrasound (US) and others. In medical imaging, an object of interest is usually selected pertaining to an area of the human body, such as the head, heart or chest.
FIGS. 1A and 1B illustrate a 3D CT image of a heart. In FIG. 1A, the image 402 illustrates the heart, while in FIG. 1B, the image 404 illustrates only the coronary arteries.
A common method for detecting coronary artery disease is to take a CT image of the chest region and quantify calcifications of the coronary artery and heart. The presence of calcifications, or calcium salts, in the vessel lining of the coronary arterial wall is a primary factor in detecting atherosclerosis, or the thickening of the artery wall, which leads to coronary artery disease. The number and amount of calcifications in particular is typically a sign of the amount of plaque, or debris, in the artery. Early detection of coronary artery disease through the use of the CT scan is a significant factor in reducing the high mortality rate of the disease.
In order to diagnose coronary artery disease using the CT scan, the number of calcifications must be identified and then “scored” in order to determine their significance. Coronary artery calcium (CAC) scoring is a time-consuming process, primarily because of the step of identifying whether each plaque is a relevant calcification and in which artery it is located. The identification step typically requires manual identification of each plaque by a cardiologist or highly-skilled technician.
A common scoring method to quantify calcifications is the Agatston Method, which provides a single score, the Agatston Score, which quantifies the total arterial calcium in the heart. Other scoring methods include volume scoring and mass scoring. In these methods and their variants, the process is essentially similar: 1) find plaques by thresholding, 2) identify whether each plaque is a relevant calcification inside a coronary artery (and if so, which artery), and 3) take a weighted sum.
Attempts to automate the calcium scoring process have been met with limited success. While some methods provide a single overall score, other methods attempt to provide individual scores for individual arteries. However, the methods for providing individual scores have trouble accurately identifying the correct artery and also detect false positives, which include irrelevant plaques (bony structures, noise, heart calcium outside vessels, etc.).
Thus, an accurate and robust method for coronary artery calcium scoring is needed.